Poly(vinylamine [PVAm] is of considerable commercial interest because of its active primary amine functionality and high water solubility. Numerous applications of PVAm and its derivatives have been demonstrated, e.g., as flocculants in waste water treatment, as carriers for non-absorbable food dyes, catalysts, and drugs, as dye acceptors in synthetic fibers; and as constituents of ion-exchange resins. The difficulty in its preparation has kept PVAm from commercialization.
Considerable research effort has been devoted to developing economic synthetic routes to PVAm. To date, the most commercially attractive synthesis for PVAm is via hydrolysis of poly(N-vinylamides) which are prepared by radical polymerization of N-vinylamides. Hydrolysis of poly(N-vinylamides) especially poly(N-vinylacetamide) [PNVA] and poly(N-vinylformamide) [PNVF], to PVAm under acid or base conditions has been reported. These traditional hydrolysis methods use excess acid or base and produce the polyvinyl ammonium acid salt with substantial amounts of carboxylic acid or the alkali metal salt of the carboxylic acid as by-products. For many applications, further purification of PVAm is required, for example, by precipitating the polymer washing and redissolving it. These additional operations significantly increase the cost and complexity of producing salt-free polymers.
U.S. Pat. No. 4,623,699 discloses linear, basic polymer powders which contain polymerized vinylamine units prepared by eliminating the formyl groups from N-vinylformamide polymer powders with a gaseous hydrogen halide in the presence of not more than 5% by weight, based on the polymer used, of water.
U.S. Pat. No. 4,578,515 discloses the preparation of N-vinylformamide from ethylidene bisformamide, which monomer is useful in the preparation of active polymers and copolymers, including poly(vinylformamide) which can be hydrolyzed to (poly(vinylamine) salts by contact with acid. These amine salts can then be converted to the free amines.
U.S. Pat. No. 4,393,174 disclosed pendant amide polymers, especially polymers containing N-vinylacetamide, N-alkyl-N-vinylacetamide, or N-vinylformamide units, which are hydrolyzed to pendant amine polymers, especially vinylamine polymers by contact with a strong aqueous base at elevated temperature.
AU-A-74529/87 discloses vinylamine copolymers and in Example 1 shows the hydrous gel of a N-vinylformamide copolymer precursor was crushed into particles, mixed with methanol and hydrolyzed with aqueous hydrochloric acid under refluxing conditions.